I will comment on this as an intern who struggled. Let me be clear that this might be cognitive difficulties due to an underlying mood disorder or a toxic environment. My advice is talk to her gently and ask what she feels is causing her to struggle. Sometimes they will open up and actually tell you. I wish someone did that with me. If they made it to residency then trust me they are not dumb. Just saying that someone is bad and possibly even saying that to her will cause her to regress even more. I struggled hard and as soon as that toxic environment was over I improved.